Global Forest Cover, Loss, and Gain 2000-2012

on November 14, 2013

Twelve years of global deforestation, wildfires, windstorms, insect infestations, and more are captured in a new set of forest disturbance maps created from billions of pixels acquired by the imager on the NASA-USGS Landsat 7 satellite. The maps are the first to measure forest loss and gain using a consistent method around the globe at high spatial resolution, allowing scientists to compare forest changes in different countries and to monitor annual deforestation. Since each pixel in a Landsat image represents a piece of land about the size of a baseball diamond, researchers can see enough detail to tell local, regional and global stories.

Hansen and colleagues analyzed 143 billion pixels in 654,000 Landsat images to compile maps of forest loss and gain between 2000 and 2012. During that period, 888,000 square miles (2.3 million square kilometers) of forest was lost, and 308,900 square miles (0.8 million square kilometers) regrew. The researchers, including scientists from the University of Maryland, Google, the State University of New York, Woods Hole Research Center, the U.S. Geological Survey and South Dakota State University, published their work in the Nov. 15, 2013, issue of the journal Science.

Key to the project was collaboration with team members from Google Earth Engine, who reproduced in the Google Cloud the models developed at the University of Maryland for processing and characterizing the Landsat data; Google Earth Engine contains a complete copy of the Landsat record. The computing required to generate these maps would have taken 15 years on a single desktop computer, but with cloud computing was performed in a few days.

Since 1972, the Landsat program has played a critical role in monitoring, understanding and managing the resources needed to sustain human life such as food, water and forests. Landsat 8 launched Feb. 11, 2013, and is jointly managed by NASA and USGS to continue the 40-plus years of Earth observations.